1. Field of the Invention
The invention relates to an all-solid-state battery that is excellent in durability.
2. Description of the Related Art
Along with the recent rapid spread of information appliances, communication appliances, etc., such as personal computers, video cameras, cellular phones, etc., the development of an excellent battery (e.g., the lithium battery) as a power source of the foregoing appliances is regarded as being important. Besides, in fields other than the information appliances and the communication appliances, for example, in the motor vehicle industry, lithium batteries and the like for use in electric motor vehicles and hybrid motor vehicles are being developed.
The lithium batteries presently available on a commercial basis employ an organic electrolytic solution whose solvent is a combustible organic solvent. Therefore, there is a need for provision of a safety device that restrains the temperature rise at the time of shortcircuit, and for improvement in structure and material for preventing shortcircuit. However, all-solid-state batteries that use a solid electrolyte instead of a liquid electrolyte allow simplification of the safety device because of the absence of a combustible organic solvent in the battery, and therefore are considered to be excellent in production cost and productivity.
In the field of the foregoing all-solid-state batteries, a sulfide solid electrolyte material has been known. For example, a non-patent literature (Fuminori Mizuno et al., “High lithium ion conducting glass-ceramics in the system Li2S—P2S5”, Solid State Ionics 177 (2006) 2721-2725) discloses a glass ceramics (sulfide solid electrolyte material) that has a composition of the system Li2S—P2S5 and a high Li ion conductivity. Furthermore, this document also discloses that cross-linking sulfur (a central portion of the S3P—S—PS3 structure) contributes to the high Li ion conductivity. Besides, Japanese Patent Application Publication No. 2005-228570 (JP-A-2005-228570) discloses a crystallized glass (sulfide solid electrolyte material) that has a composition of the system Li2S—P2S5 and a high Li ion conductivity. Furthermore, the Japanese Patent Application Publication No. 2005-228570 (JP-A-2005-228570) also discloses that when the crystallized glass is to be fabricated, the amount of Li2S is 68 mol % to 74 mol %, and the amount of P2S5 is 26 mol % to 32 mol %, and the sintering is performed in the temperature range of 150° C. to 360° C. Besides, the crystallized glass described in this patent application publication (JP-A-2005-228570) has cross-linking sulfur, similar to the foregoing glass ceramics.
Sulfide solid electrolyte materials that have a cross-linking chalcogen represented by the cross-linking sulfur have a problem of being liable to decompose due to the reaction with the positive electrode active material and therefore having low durability while having an advantage of having high ionic conductivity.